The goal of this proposal is to launch an investigative program focused on neural and endocrine factors timing puberty in a male mammal, the ferret. Experiments are designed to develop an animal model of male puberty. As such, the proposed studies represent a novel paradigm for determining the neuroendocrine basis for the onset in testis function, namely, the ontogenetic transformation of a discontinuous pattern of luteinizing hormone (LH) secretion by the neuroendocrine system. The specific aims of my research are to: 1) characterize moment-to-moment fluctuation in blood LH concentrations through puberty and correlate the pattern of LH secretion with two key markers of testis function, steroid hormone secretion and spermatogenesis; 2) define the separate roles played by gonadal steroid hormones and hypothalamic maturation as the neuroendocrine mechanisms underlying the pubertal changes in LH patterns; 3) establish the physiological significance of temporal oscillations in pituitary LH release in shaping the onset of testis function; and 4) localize the hypothalamic structure(s) directing the periodic discharge of LH by the pituitary gland. The proposed studies are novel and important. First, they stand in sharp contrast to past studies which have relied on cross-sectional comparisons of the average concentration of reproductive hormones in groups of animals. Second, these studies are important because current explanations of the neuroendocrine basis of puberty are not performed from the standpoint of shaping target organ function by modulating the amplitude, frequency, and duration of pituitary gonadotropin secretion. Finally, the implications of the proposed studies for clinical investigations are profound because they seek to define the temporal limits of hypothalamic-pituitary signaling which initiate steroidogenesis and spermatogenesis, and the neural structures directing periodic oscillations in the trophic signal supporting the onset of the endocrine and exocrine function of the testis.